Trigger a web app installation when a web app is installed in ARC.

This CL allows ARC to inform ArcAppListPrefs whether a newly installed
package is a web app or not. If it is a web app, ArcAppListPrefs
requests the web app's data from ARC, and upon receiving the data,
triggers an installation of the web app.

BUG=893927

Change-Id: Ia88043ef1d01f709e82340326e81de01da6c1c4c
Reviewed-on: https://chromium-review.googlesource.com/c/1314068
Reviewed-by: Dominic Battré <battre@chromium.org>
Reviewed-by: Ben Wells <benwells@chromium.org>
Reviewed-by: Yury Khmel <khmel@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Greg Kerr <kerrnel@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: David Jacobo <djacobo@chromium.org>
Commit-Queue: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613031}
18 files changed